Many of the fundamental questions aimed at understanding the physiology and, particularly, the pathophysiology of the myocardium are now being addressed at the cellular level using isolated cardiac muscle cells, or myocytes. The principal aim of this application is to develop simple and economical digital imaging tools that the cardiac muscle research community can use to record the biomechanical properties of myocytes during muscle contraction. The project will be undertaken as three Specific Aims for the development of: (1) High-Rate Digital Image Acquisition for visualization the contracting cardiac myocyte, (2) Software-Based Myocyte Cell Length Recording to perform real-time analysis of digital image data to dynamically characterize, display and save the cardiac myocyte cell length data on-line, and (3) Sarcomere Length Recording expands on the methods of high-rate image acquisition and numerical analysis to quantify the sarcomere length in real-time during muscle contraction. These methods fundamentally improve on existing techniques in terms of functional capability and simplicity of use. In commercialized form the instrumentation systems envisioned are also economical and thus accessible to many more laboratories interested in pursuing cardiac muscle research questions at the cellular level.